Technical review of the energy and protein requirements of growing pigs: energy

A review of work reported in the literature was used to present quantitativ e descriptions of energy dispositioning in the growing pig. These are detai led in the text, which points to preferred values, as well as to anomalies and lacunae. The review was prepared with the objective of allowing from it s content the inclusive and quantitative modelling of energy requirement. R equirement is approached as the sum of the component factors; maintenance, protein retention and lipid retention. Conventional expressions of maintena nce requirement, as some function of pig mass, were found unconvincing in t heir variety of expression of coefficients and exponents. The review conclu ded that maintenance is properly related to protein turn-over, and thereby requires at least to include elements of concomitant protein metabolic acti vity. It was also judged that maintenance costs might be farm-specific. The energy requirements for activity, gaseous losses and disease were identifi ed as important, but unsatisfactory in their quantification. Exploration of the energy costs of uncomfortable ambient temperatures suggested that whil st the responses of the pig are open to sophisticated and relatively exact calculation, the description of comfort remained inexact. The efficiency of retention of lipid by direct incorporation was high and may comprise a sub stantial proportion of the dietary lipid supply. There was little evidence of variation in the efficiency of utilization of metabolizable energy from carbohydrate for lipid retention. The linear-plateau paradigm for protein r etention was adopted. The efficiency of utilization of energy for protein r etention measured by a variety of approaches was found to be highly variabl e, prone to error and the literature confused. It was concluded that the ef ficiency of use of metabolizable energy for protein retention would be a fu nction of at least: (a) the absorbed substrate being metabolized for the sy nthesis of body protein, (b) the rate of total protein tissue turn-over ass ociated with the retention of newly accreted protein and not already accoun ted in the estimate of maintenance, (c) the mass of protein tissue involved in turn-over, and (d) the degree of maturity attained, and any influence m aturity may have upon the rate of turn-over of total body protein. Algorith ms for energy requirement are presented based upon protein turn-over and th ese appear to have some consistency with empirical findings.